This disclosure relates generally to imaging systems, methods and apparatus, and more particularly to volume holographic imaging systems, methods and apparatus that obtain enhanced images from multiple depths within an object.
Microscopic imaging systems are beneficial for biomedical and clinical applications. Three dimensional microscopic imaging systems, such as confocal microscopy and optical coherence tomography (OCT) have been developed to detect tissue structures within biological samples. Both confocal microscopy and OCT require mechanical, opto-electronic, or acousto-optic scanning in two lateral and axial dimensions.
Volume holographic multiplexing (VHM) has been developed to eliminate the need for mechanical, opto-electronic, or acousto-optic scanning. In VHM, holographic gratings are superimposed in a volume recording material such that each grating obtains depth resolved information from different depths within the object. Microscopic imaging systems incorporating VHM visualize features of the object at different focal planes, for example, tissue structures at different focal planes. Each focal plane within the object can be projected to a different lateral location on a camera. Thus, the entire object volume is imaged slice-wise onto the camera without the need for scanning. VHM imaging systems have many useful applications such as spectral and three dimensional biological imaging (hereafter four-dimensional (4D) imaging), endoscope imaging systems, spectrometers, and the like.
Conventionally, VHM utilizes a spectrally broadband source to illuminate objects of interest. If objects of interest are illuminated by a spectrally broadband source, the contrast in VHM systems is reduced because colors originating at multiple depths cannot be separated due to the degeneracy properties of the hologram.